Here in San Francisco, 49ers fans are still stinging from their football team’s defeat up in Seattle last Sunday. But there’s no denying reality: the stage has been set for Super Bowl XLVIII between the Denver Broncos and the Seattle Seahawks.

One of the popular stories during the two-week lull before the big game is the impressive comeback of Broncos quarterback Peyton Manning. After two major neck injuries in the 2006 and 2010 seasons, Manning was thought to be all washed up. Instead he’s had a record-setting season.

Manning’s Super Bowl bid and comeback from injury have also prompted the revisiting of his decision to get an experimental stem cell treatment in Germany in September of 2011. On Tuesday, the title of an article carried by Voxxi.com asked, “Peyton Manning: Did stem cells save the quarterback’s career?”

Your answer might be “yes” just watching Peyton’s return to elite status. But the details provided in the article show that there’s no solid evidence that his trip to Europe had any benefit to him or helped advance the stem cell field as a whole.

Manning’s treatment apparently involved the harvesting of stem cells from his own fat tissue (probably from his belly) that was injected into his neck. This procedure is not approved in the United States and it’s unclear whether the right type of cells is even present to have any beneficial effect. It’s likely that this fat tissue contained mesenchymal stem cells, an adult stem cell which can form bone, cartilage, fat, or muscle.

It’s potentially dangerous to inject uncharacterized stem cells that haven’t been matured into a specialized cell type. Recently a case of an untested cosmetic stem cell treatment grabbed the headlines in which the patient’s mesenchymal stem cells were injected around the eyes. Three months later pieces of bone formed in the patient’s eyelids causing excruciating pain.

All of this is to say that there’s a reason the Food and Drug Administration (FDA) requires a lengthy, rigorous process to begin and then run clinical trials for the approval of any stem cell-based treatment (or any drug for that matter): to provide evidence that the therapy is safe and effective in a large cohort of patients.

To people who are currently suffering from incurable diseases, these clinical trials can’t happen fast enough and can lead them to look upon Manning’s case with false hope. Larry Goldstein, a CIRM grantee and director of the UC San Diego Stem Cell Center, is quoted in the article and echoes this theme:

When a highly visible celebrity athlete chooses to undergo an untested/unproven therapy, and if they happen to get better without knowing whether the therapy is what caused the improvement, they encourage many other people to ignore scientific evidence and to substitute hope and blind trust for proof. The downside is that many people might be hurt by subjecting themselves to a risky procedure, or procedure with unknown risks, when there is no evidence of benefit to be gained.

Ultimately, Manning had a cervical spinal fusion surgery, which makes it even murkier what impact the stem cell therapy had on his spectacular season. So while I’ll be rooting for Peyton when he steps onto the field a week from Sunday, my hope is that people won’t follow in his footsteps to try unregulated and unproven stem cell therapies. As the article sums up quite firmly in its conclusion:

It is important for the public to understand there are legitimate reasons stem cell therapy is not yet approved for spinal injuries, and even though Peyton Manning has had a phenomenal career post-surgery and therapy, none of it can yet be attributed to the stem cell injections, regardless of what supporters of the treatment may indicate.